Preparation, Characterization and CO Oxidation Performance of Ag2O/γ-Al2O3 and (Ag2O+RuO2)/γ-Al2O3 Catalysts

Abstract

This research dealt with the preparation and characterization of silver oxide (SLO) nanomaterials (NMs) and their composite catalysts (i.e., silver and ruthenium oxide (SLORUO)). The prepared materials were tested for their catalytic performance in carbon monoxide (CO) oxidation. Generally, silver in its pure state is not widely used for CO oxidation due to stability and structural issues. However, the usage of subsurface oxygen and oxygen-induced reconstruction could be effective as an oxidation catalyst at a slightly high temperature. The low-temperature reaction of highly active RuO2 (RUO) is a well-known phenomenon. Thus, the possibility of using it with SLO to observe the combined catalytic behavior was investigated. The wet chemically prepared SLO and SLORUO NMs exhibited spherical and rods in spherical aggregate-type surface morphology belonging to cubic and rutile crystalline structures, respectively. The NMs and catalysts (i.e., the NMs on γ-Al2O3 catalyst support at 0.5 and 1.0 wt.% ranges) showed good thermal stability. The dry and wet CO oxidation using RUO and SLO showed concentration-dependent catalytic activity. The RUO, SLO, and SLORUO composites using 0.5 wt.% showed full CO oxidation at 200, 300, and 225 °C, respectively. The reasons for the observed activity of the catalysts are explained based on the pore characteristics, chemical composition, and dispersion using H2 temperature-programmed reduction (TPR) behaviors.

Ruthenium Catalyst Supported on Multi-Walled Carbon Nanotubes for CO Oxidation

“…Authors suggested that the CO molecule directly reacts with a surface O atom neighboring the Pd dopant, leading to the formation of CO 2 and a surface O vacancy, without any activation energy. Ananth et al [43] studied the CO oxidation on RuO 2 /Al 2 O 3 catalyst, and showed complete CO oxidation at 200˚C, 225˚C, and 300˚C, similar to these results obtained for the same temperature range and at space velocity between 2000 and 2657 (mL/min.g). Therefore, it can be attributed to the high distribution and dispersion of metal oxide over an MWCNT, due to the high surface area, which influences the CO 2 selectivity.…”

“…Results showed graphitic carbon at 284.3 eV [41]. Peaks at 284.5 and 290.5 eV are assigned to the carbon atoms (C-C) attached to groups containing oxygen (C=O) in their structure [43]. The electronic transition of orbitals π → π* was associated with the peak at 290.5 eV.…”

Thermal CO Oxidation and Photocatalytic CO2 Reduction over Bare and M-Al2O3 (M = Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au) Cotton-Like Nanosheets

“…For Ag-Al2O3 nanosheets, Ag 3d3/2 and Ag 3d5/2 XPS peaks were observed at BEs of 374.5 eV and 368.6 eV, respectively. This was attributed to metallic Ag [6,32,36]. The shoulder [15,31,32].…”

“…Aluminum oxide (Al 2 O 3 ) has extensively been used as a heterogeneous catalyst in diverse catalytic reactions of CO oxidation [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], CO 2 reduction [20][21][22][23], CO 2 methanation/hydrogenation [20,[24][25][26][27], and preferential oxidation of CO [28,29]. The efforts to increase the catalytic activity of the metal oxide have been devoted to the modification of the metal surface by loading of transition metals in groups of 9 (Co, Rh, and Ir), 10 (Ni, Pd, and Cu), and 11 (Cu, Ag, and Au).…”

“…They reported that Ni showed an unexpectedly higher CO oxidation activity than the Pd. Ananth [6]. Han et al reported a high CO oxidation activity at 30 • C for NiO (≤1 nm) on mesoporous Al 2 O 3 prepared using atomic layer deposition [16].…”